package com.atguigu.encryption.utils;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class SHA1 {

    public static String getSha1(String str) {
        if (null == str || 0 == str.length()) {
            return null;
        }
        char[] hexDigits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
        try {
            //创建SHA1算法消息摘要对象
            MessageDigest mdTemp = MessageDigest.getInstance("SHA1");

            //使用指定的字节数组更新摘要。
            mdTemp.update(str.getBytes("UTF-8"));

            //生成的哈希值的字节数组
            byte[] md = mdTemp.digest();

            //SHA1算法生成信息摘要关键过程
            int j = md.length;
            char[] buf = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = md[i];
                buf[k++] = hexDigits[byte0 >>> 4 & 0xf];
                buf[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(buf);
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return "0";
    }

}